1. Field of the Invention
The present invention relates to an office chair in three dimensions, particularly to one that is formed in one-piece structure of composite plastic materials with an adjusting apparatus.
2. Description of the Related Art
A conventional office chair 10 as shown in FIGS. 1A and 1B comprises an underframe portion 11, a seat portion 12, a back portion 13 and two armrests 14, among which the seat portion 12 is the key to be composed with other components. The seat portion 12 of a conventional office chair 10 includes a metal plate 121 combining with a seat pad 122, and the bottom thereof combines a supporting device 123 to mount on a middle column 111 of the underframe portion 11. Besides, the metal plate 121 links up two connection seats 124 on both left and right sides to fix on the armrests 14. With such structure of multi components combination, a conventional office chair 10 is constructed in a complicated method whereby the finished product lacks unity and firmness, plus the heavy weight of metal materials; there is still room for improvements.
On the other hand, a conventional chair made of plastic has a lightweight advantage but the simple structure is more suitable for outdoor activities than offices.
FIGS. 2A and 2B illustrated a one-piece structure of a conventional office chair disclosed in the U.S. Pat. No. 7,887,138. The seat base 10a of the invention is made of one-piece plastic material and mainly comprises a middle axle seat 101, a claw member 102 with a plurality of arched supporting arms 103 extending upwards from the rim of the middle axle seat 101 in the shape of claws, and a base frame 104 formed at the top of the supporting arms 103 of the claw member 102. Such structure features the invention an easy and rapid assembly with stable structure and light weight. However, the arched supporting arms 103 are arranged all over under the base frame 104, resulting the invention in a rigid status without ant flexibility.
Also, the U.S. Pat. No. 7,637,570 disclosed a chair invented by Wilkhahn that has a seat and a seat mechanism, where the seat mechanism includes two supporting arms arranged on both sides of the chair and functioning individually, and the seat is fixed on the supporting arms so that when the seat is tilting sideways, the other side would not be influenced and lose balance. However, the invention includes a plurality of rigid supporting arms and ball joints to achieve the sideway function, therefore leading to a much more complex structure.